Kurzbeschreibung
(Englisch)
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Assessing the impacts of anthropogenic climatic change on the growth and distribution of tree species requires a good knowledge of the climatic, edaphic and synecological controls acting upon each individual species. Regarding European beech (Fagus sylvatica), there is conflicting evidence on the drought response along latitudinal vs. altitudinal gradients. We aim to answer three questions in this context: (1) What is the functional form of the relationship between drought and growth of beech? (2) Have the growth patterns of beech changed due to recent climatic changes close to the dry distribution limit? (3) Do beech trees of different geographical regions (originating from different phylogeographical lines) show a different response to site conditions close to the dry distribution limit? Tree-ring analyses have hardly ever been used to study the influence of soil moisture and nutrient availability on the growth potential and distribution range of individual tree species. In this project, we will use tree-rings for the first time to analyse the relative influence of different site factors – not only climatic but also edaphic – on the growth potential and drought sensitivity of beech at its dry distribution limit. A combination of dendroecological and soil ecological analyses at five pairs of sites in Switzerland, France and Spain will provide valuable input for assessing the ecophysiology of European beech populations and their sensitivity to changes in climate. Tree growth and sensitivity patterns at field plots close to the dry distribution limit of beech will be compared to mesic plots close-by that experience the same regional climate but better edaphic (moisture and/or nutrients) conditions. A morphological characterisation of the sample trees will be performed in addition to the dendroecological characterisation.
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Partner und Internationale Organisationen
(Englisch)
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AT, BE, BG, CH, CZ, DE, DK, ES, FR, GR, HR, HU, IE, IT, NL, PL, RO, RS, SE, SI, SK, UK
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Abstract
(Englisch)
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Pascale Weber1, Harald Bugmann2, Lorenz Walthert1, Andreas Rigling1 1Swiss Federal Research Institute WSL, 8903 Birmensdorf, Switzerland; 2Forest Ecology, Institute of Terrestrial Ecology, Swiss Federal Institute of Technology ETH, 8092 Zurich, Switzerland Beech (Fagus sylvatica L.) covers a large area mainly in the colline and montane ranges of Europe, and a drier and warmer climate, as expected for the coming decades, is likely to alter its distribution. So far, an altitudinal shift has been projected using a variety of modelling approaches. However, we lack knowledge about the climatic and edaphic factors that control the growth and competitive behaviour of beech at its dry distribution limit. In this project, we applied and further developed dendroecological methods to study the drought response and sensitivity pattern of beech at sites with different moisture regimes. Specifically, we compared three pairs of sites from different geographical regions at the climatic dry distribution limit of beech in Switzerland, including one site on a dry and one on a mesic soil each. The adaptation of radial growth to water availability was found to differ between moderate and dry sites, in that average ring-width at moderate sites was around double the width at dry sites. For the whole study period between 1930 and 2006, the sites with lowest available water capacity (AWC) were found to respond most sensitively to drought. However, in recent years, sites with higher AWC showed increasing drought sensitivity, i.e. responded even more strongly to drought than the dry sites. This change in sensitivity was found to run parallel to a seasonal shift in drought response at moderate sites, with different months getting more important for drought response in the three studied regions. Whereas dry sites generally showed more negative pointer years than moderate sites, it appears that the frequency of pointer years has increased at moderate sites, i.e. that moderate sites have become particularly more sensitive in the last quarter of the 20th century. Yet, the frequency of pointer years at the dry sites has remained fairly constant. These results indicate that dry forests at the limit are probably already adapted to extreme conditions, while changes in the growth patterns of moderate forests have to be expected.
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